The present invention relates to a pneumatic pressure regulating valve arranged in the path of a gas line, the opening of which can be automatically changed by means of said pressure regulating valve in relation to the differential pressure between a reference pressure and one or more gas pressures applied to at least one inlet of said regulating valve, wherein a control diaphragm is provided in the pressure regulating valve, said control diaphragm being, on the one hand, subjected to the reference pressure and, on the other hand, to the gas pressure or gas pressures as well as to a governor spring, wherein a change in the differential pressure between the regions adjacent to the control diaphragm causes an adjustment of the control diaphragm and the control diaphragm itself or a closing element actuated by the control diaphragm increases or reduces the opening through an outflow cross-section of the pressure regulating valve, and wherein a structure of the pressure regulating valve that is arranged adjacent to the outflow cross-section on the diaphragm side forms a stop for the control diaphragm or for the closing element actuated by the control diaphragm in the latter's closed position.
A pneumatic pressure regulating valve designed as a throttle valve for automatically controlling the pressure in the crankcase of an internal combustion engine and comprising the elements mentioned above has been disclosed in DE 200 16 214 U1. This known throttle valve is provided such that it comprises two power elements for generating the return force acting on the control diaphragm, wherein a first power element exerts its return force on the control diaphragm over the entire travel distance of said control diaphragm, and wherein a second power element exerts its return force on the control diaphragm only over the second section of the travel distance of said control diaphragm, wherein said second section of the travel distance is the distance between a partially open position and the closed position of said control diaphragm. It is, furthermore, preferably provided that the two power elements are formed by two springs, the first of which is in permanent operable engagement with the control diaphragm and the second of which enters into operable engagement with the control diaphragm only after a first section of the travel distance of the control diaphragm has been covered in closing direction. Preferably, the two springs are helical springs of varying length.
This known throttle valve is considered to be to disadvantage in that the use of two springs requires a further spring which has to be manufactured and installed in addition. In this case, a higher number of components and increased manufacturing and assembling efforts, thus, have to be paid for the improved control characteristic achieved by means of the two power elements. What is more, this known throttle valve is to disadvantage in that the tolerances of the various components, here the springs, are adding up, with the result that the overall arrangement is more imprecise.
An alternative executive form of said known throttle valve according to DE 200 16 214 U1 provides that one power element is formed by a spring and that the other power element is the control diaphragm itself, said control diaphragm being provided with its own return force or with an integrated power element. While it is true that this prevents the requirement of a separate second spring, it has turned out that it is difficult to produce the control diaphragms which are suitable for this executive form of the valve and comprise their own exactly defined and permanently constant return force or an appropriately acting integrated power element.
A third version of this known throttle valve comprises instead of the two power elements one power element that exerts at least two different return forces and exerts a first return force on the control diaphragm over a first section of the travel distance of said control diaphragm and exerts a second higher return force on the control diaphragm over a second section of the travel distance of said control diaphragm. Theoretically, this executive form is a more elegant solution because it requires only one power element, but it has, here as well, turned out to be difficult to reproducibly manufacture such a power element and integrate it in the throttle valve, said power element having two return forces which are different in their relation to the travel distance.